Lorus Therapeutics Inc. to present critical results for lead antisense anti-cancer drug at ASCO-- GTI-2040 reaches clinical endpoints

TORONTO, ON – May 9, 2001 - Lorus Therapeutics Inc. (TSE: LOR; OTCBB: LORFF) announced today that its lead antisense anti-cancer drug, GTI-2040, will be the topic of a presentation at the annual meeting of the American Society of Clinical Oncology (ASCO), May 12-15, 2001 in San Francisco. The presentation is entitled “Phase I Study of GTI-2040 Given by Continuous Intravenous Infusion (CVI) in Patients with Advanced Cancer.”

The presentation, to be given by Dr. Richard Schilsky, principal investigator, Professor of Medicine and Associate Dean for Clinical Research at the University of Chicago, Division of the Biological Sciences, will provide an overview of the open label, single center, dose escalating study which involved 28 patients with advanced or metastatic solid tumors or lymphoma. GTI-2040 met its Phase I clinical endpoints of safety and tolerability and the recommended Phase II dose was identified. Based on the promising results of this study, the drug will be further investigated in combination chemotherapy in Phase II clinical trials.

“The positive data obtained in pre-clinical studies and in this Phase I clinical trial provides a solid basis for Lorus to advance GTI-2040 to Phase II trials,” stated Dr. Jim A.Wright, president. “Dr. Schilsky is familiar with the mechanism of action of antisense compounds and is a key participant in developing the encouraging potential of GTI-2040 for the management of cancer.”

In pre-clinical testing, previously reported, GTI-2040 demonstrated strong anti-tumor properties when tested against a wide range of human tumors in mouse models, including tumors derived from the lung, breast, prostate, colon, liver, ovary, kidney and pancreas. Significant inhibitions of tumor growth, disease stabilizations and in some cases, dramatic tumor regressions were observed.

ASCO’s Annual Meeting is considered to be the premiere event in clinical oncology worldwide and draws substantial attendance from around the world. The meeting provides oncology professionals with the most current information available on recent advances in cancer research, prevention, and treatment.

About Lorus

Lorus is a biopharmaceutical company focused on the research and development of cancer therapies. Lorus’ goal is to capitalize on its research, pre-clinical, clinical and regulatory expertise by developing new drug candidates that can be used, either alone, or in combination, to successfully manage cancer. Through its own discovery efforts and an active acquisition and in-licensing program, Lorus is building a portfolio of promising anti-cancer drugs. Late-stage clinical developments and marketing will be done in cooperation with strategic pharmaceutical partners. Founded in 1986, Lorus Therapeutics Inc. is a public company listed on the Toronto Stock Exchange under the symbol LOR, and on the OTC BB exchange under the symbol LORFF.

Except for historical information, this press release contains forward-looking statements, which reflect the Company’s current expectation regarding future events. These forward-looking statements involve risks and uncertainties, which may cause actual results to differ materially from those statements. Those risks and uncertainties include, but are not limited to, changing market conditions, the successful and timely completion of clinical studies, the establishment of corporate alliances, the impact of competitive products and pricing, new product development, uncertainties related to the regulatory approval process, and other risks detailed from time-to-time in the Company’s ongoing quarterly filings, annual information form, annual reports and 40-F filings.

Lorus Therapeutics Inc.’s press releases are available through the Company’s Internet site: http://www.lorusthera.com.

ABSTRACT:

PHASE I STUDY OF GTI-2040 GIVEN BY CONTINUOUS INTRAVENOUS INFUSION (CVI) IN PATIENTS WITH ADVANCED CANCER

L. Janisch, R.L.Schilsky, N.J. Vogelzang, T.M. Zimmerman, D. Fitsialos, G. Ely, M.J. Ratain, University of Chicago, Chicago, IL, USA, and Lorus Therapeutics, Inc., Toronto, Ontario, Canada

GTI-2040 is a 20-mer phosphorothioate oligonucleotide that is complementary to the R2 subunit of ribonucleotide reductase. GTI-2040 inhibited the growth of several xenografts, particularly renal cell carcinoma, at doses of 0.5-30 mg/kg given for 2-4 weeks. Toxicology studies in rodents and monkeys revealed hemodynamic effects, bone marrow suppression and complement activation. This initial phase I trial administered GTI-2040 as a 21 day CVI. Eligible patients (pts) were >18 years; had a solid tumor or lymphoma for which no effective therapy was available; performance status (KPS) >70; no cancer therapy within 4 weeks; adequate organ function and normal coagulation (coag) tests. All pts provided written informed consent. GTI-2040 was administered via central venous catheter by a portable infusion pump that was refilled weekly. A cycle of treatment was a 21day CVI followed by one week of rest. The starting dose was 18.5 mg/m2/day (approx. 0.5 mg/kg/d), corresponding to 1/10 and 1/6 the dose that produced minimal toxicity in rodents and monkeys, respectively. Doses were doubled in cohorts of 1-3 pts until the appearance of >Gr 1 toxicity, with subsequent escalation of 20-30% in cohorts of > 3 pts. DLT was defined as Gr 4 neutropenia lasting > 3 days or with fever; Gr 4 thrombocytopenia (T) or Gr 3 T with > Gr 1 bleeding; or > Gr 3 non-hematologic toxicity despite maximal supportive care. Thus far, 14 pts (10 M, 4 F) have been enrolled at dose levels of 18.5-148 mg/m2. Median age is 65 y (range 27-78); median KPS 80 (range 70-100). Diagnoses are: colon, renal, mesothelioma, pancreatic, lung, liver, lymphoma, sarcoma and unknown primary. One pt experienced dose-limiting fatigue (Gr 3) at 148 mg/m2. Other toxicities have included anorexia, nausea, hypotension, chills and fever. Accrual continues at 185 mg/m2/day. PK analysis is ongoing.